1. Field of the Invention
The present invention relates to a display device, and more particularly, to an active matrix display device in which a drive circuit (peripheral circuit) is also formed on the same substrate on which a display region is formed.
2. Description of the Related Art
Such a type of display device is referred to as a so-called drive circuit integral type display device, and has a structure being effective for downsizing.
Pixels each having a switching element are arranged in matrix on a display region of the display device. In order to write image data into a pixel, the switching element of the pixel is turned on. While the switching element is in an on-state, a signal supplied from the drive circuit is written as the image data into the pixel.
The switching element includes a thin film transistor. The drive circuit includes a large number of thin film transistors. The thin film transistors of the respective pixels and the thin film transistors of the drive circuit are normally formed side by side.
As also described in, for example, JP 2004-242084 A, a drive circuit including a level shift circuit has been known. The level shift circuit eliminates an inconvenience that a voltage level of an input signal from an external device is different from a voltage level of a circuit in the display device.